Hydraulic materials provide cured articles excellent in strength, durability, and the like. Accordingly, the hydraulic materials have been widely used as cement compositions such as a cement paste, a mortar, and a concrete. The hydraulic materials are indispensable for the construction of civil engineering and architectural structures.
After having cured, the hydraulic materials may cause the dissipation of unreacted moisture remaining in the materials depending on, for example, ambient temperature and a humidity condition. As a result, such a problem that drying shrinkage progresses and hence each of the cured articles cracks to reduce its strength or durability arises. Reductions in strength, durability, and the like of each of the civil engineering and architectural structures cause serious problems such as a reduction in safety and an increase in repair cost.
Legal regulations against such problems have become increasingly stringent. The cracking of a concrete is also an object of defect liability in a law established in June 1999 concerning the promotion of the securing of housing quality. In the Japanese Architectural Standard Specification for Reinforced Concrete Work revised in February 2009 (JASS 5 (Architectural Institute of Japan)), a shrinkage strain in a concrete with long-term durability (100 years or more) at a 26th week was restricted to 800×10−6 or less.
Emphasis has been recently placed on shrinkage-reducing agents for hydraulic materials as means for reducing the drying shrinkage of cured concrete articles. Architectural Institute of Japan is scheduled to establish criteria concerning the shrinkage-reducing agents for hydraulic materials simultaneously with the revision of the JASS 5 described above.
An alkylene oxide adduct of an alcohol having 1 to 4 carbon atoms (see Patent Literature 1), an ethylene oxide and propylene oxide co-adduct of a polyhydric alcohol having two to eight hydroxyl groups (see Patent Literature 2), an alkylene oxide adduct of a lower alkylamine (see Patent Literature 3), a polypropylene glycol in an oligomer region (see Patent Literature 4), low-molecular weight alcohols (see Patent Literature 5), and an alkylene oxide adduct of 2-ethylhexanol (see Patent Literature 6) have been reported as the shrinkage-reducing agents for hydraulic materials. However, those shrinkage-reducing agents for hydraulic materials each involve the following problem. When each of the agents is used in a concrete, the strength of the concrete reduces. Accordingly, the ratio of a cement paste is requested to be increased in order that the strength may be secured. As a result, such a problem that a cost for the concrete increases arises.
Alkylene oxide adducts of polyhydric alcohols having two to eight hydroxyl groups have been reported as shrinkage-reducing agents for hydraulic materials, each of which is capable of suppressing a reduction in strength when used in a concrete (see Patent Literatures 7 and 8). However, each of those shrinkage-reducing agents for hydraulic materials requires a combination with any other admixture such as a powder resin or an expansive additive, and hence has been unable to solve the problem, i.e., the increase of the cost for the concrete.